Tuesday, 11 February 2003
Simulated surface hydrology and energy balance of West Africa using SSiB with observed precipitation and satellite-derived vegetation
This paper discusses the climatology and modeled surface hydrology and energy balance in West Africa. Since precipitation in this region is of prime importance, it will be the main driver of the simulation. For this study, 28 sites within West Africa were selected based on precipitation data that was available with a complete record for an eleven-year study period from 1982 to 1992. The remaining forcing variables were derived from National Center for Environmental Protection reanalysis data (NCEP, 2002) and interpolated from 6-hour values to hourly values during this time period. The land cover map used to determine standard surface parameter values was from the global land cover database of Hansen et al (2000). Leaf area index and vegetation cover parameters were derived from available AVHRR NDVI satellite data (Los et al, 2001).
To investigate the surface fluxes in the region, numerical experiments are conducted with an offline version of the model, SSiB. This analysis describes the temporal and spatial pattern of the water and energy balance and examines the inter-annual variability of these fluxes based on the annual precipitation. In addition, a study of the importance of land surface characteristics on the land surface-atmosphere relationship is conducted. This study draws a comparison between the use of satellite-derived data and a set of standard data collected from surveys. Finally, the impacts of heterogeneity of vegetation type and resolution of vegetation data on model output are discussed.